very good post and summary. sadly, it seems blizzard is running out of ideas.Incanter's Ward was already relatively close to the others in terms of dps so this change makes it very attractive. This proves once again how flawed the lvl 90 mage talents really are. They are now three different ways of increasing your dmg 15% all with 100% uptime in theory.
Rune of power is a flawed to the core, this thing would require you to stand still for an entire fight and is very clunky, this talent had only ever been attractive to arcane and worthless to the other speccs. This ability cripples your movability and makes the hunters old Sniper training look easy on the mobility. This ability should be removed or made into a arcane cooldown with maybe a 15 seconds duration.
Invocation is something that makes you cast something just to keep up a buff, much like rogues old Hunger for Blood. Blizzard removed Hunger for Blood because they didn't like the "have to cast something just do keep a buff up" and they should remove invocation as well.
Incanter's Ward feels much like the old Owlkin Frenzy, where you will willingly stand in fire or take damage to increase your damage, which was also something blizzard stated long ago was not a playstyle they didn't like.
They should simply scrap the 90 talents completely and make something fun there instead, getting your 90 talent should be something fun and special and it kinda is for most classes. When I leveled to 90 with my mage the feeling I got was "Oh crap, now I have to deal with one of these hassles." I know it's too late for a chnage this far into the expansion but for next one I hope blizzard just scrap the 90 talents all together.